Abstract: Fractionation effects were corrected by empirical (K correction) and double-dilution methods in isotopic measurements of 1—50 ng lead standard sample. Results showed that the relative deviations of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb could be reduced from 0.1%—0.6% to 0.02%—0.38% for Pb sample more than 10 ng using empirical methods, and using double-dilution methods it could be reduced from 0.08%—0.45% to 0.001%—0.14%. But no obvious effect were detected for Pb sample less than 10 ng of two methods, which implied other facetors that affceted the precision besides fractionation effects.